Applicant has uncovered and addressed in prior art patents a significant problem in the construction of a disk brake caliper that can be submerged, see U.S. Pat. Nos. 7,125,084; 7,185,955; 7,226,133; 7,740,036 and other patents pending. By way of background, a conventional boat trailer utilizes a fixed axle secured to a trailer frame. A wheel assembly is coupled to the axle by use of a wheel hub. The wheel hub employs bearings, namely inner and outer bearings with an associated inner and outer race, which permits rotational movement in relation to the axle. Proper lubrication of the bearings is critical in controlling heat and premature bearing wear. Larger trailers require a braking system which can further add to the heat buildup.
Problems with the wheel assembly are pronounced with the trailers are placed in water, such as when loading or unloading a boat. The heat build-up during normal operation of the trailer (i.e. bearing rotation and brake application) can result in the brake hubs heating up to a temperature that no coating can be applied. This is especially true of disk brakes wherein the disk brake caliper is made of conventional steel. Such disk brake calipers, when subjected to an immediate quenching after trailering, can quickly corrode. Further, the cylinder wall holding the piston and brake pad against the rotor can quickly corrode. The result is a dragging brake which creates a high heat problem, which can not only affect the life of the bearings and brakes, but can lead to a dangerous condition wherein either the bearings break down or the rotor heats up so much that the brakes will not work. While calipers made from high quality stainless steel can be used to lessen corrosion, it is prohibitively expensive for the average consumer. Further even if the piston is made of high quality stainless steel, and the caliper made of high quality steel, corrosion around the piston on the cylinder wall will result in brake dragging.
The problem to be addressed occurs when a conventional brake caliper is left in the elements to corrode, or is subjected to salt water immersion which expedites such corrosion. Corrosion of the piston and cylinder in the disk caliper can induce a very high frictional load and, in a worse case scenario can literally freeze the piston and brake pad in a fixed position and lock the rotor in position. Brake dragging is common and leads to the red hot glowing hubs that can be seen at night as an unsuspecting vehicle operator is pulling an affected trailer. Should the bearing fail, the bearing and race will typically disintegrate with a likely result of the hub and wheel detaching from the axle of the trailer. Another scenario that happens is the brake caliper's piston will not retract due to the corrosion creep around the piston's cylinder wall and the brake pads lock onto the rotor and wheel to where the tire drags and causes flat spots or wear through the tire entirely causing the tire to become flat.
Attempts to prevent corrosion of the piston and cylinder walls include the use of a dust boot and sealing rings in an effort to protect the brake piston cylinder assemblies from contamination and corrosion. However, these devices can actually trap moisture within leading to premature failures. Boat trailers present an excellent example of premature rotor wear as a boat trailer must be inserted into the water for loading or unloading of the boat which can quickly lead to a locking of the brake piston.
U.S. Patent Application 2013/0192936 to Scotti, et al., discloses a flexible sheathing for the protection of piston-cylinder units for disk brakes. Such flexible sheathing may be arranged in a retracted condition wherein the piston is completely accommodated within the cylinder and in an extended condition wherein the piston is completely extracted from a caliper body defining the cylinder.
U.S. Pat. No. 7,097,004 to Barrett, et al., discloses a boot-type seal having a seal and a valve. The seal has a first seal member, which is configured to sealingly engage a first surface, and a second seal member, which is configured to sealingly engage a second surface.
U.S. Pat. No. 4,503,947 to Heidmann, et al., discloses the open bore of a disc brake caliper assembly is protected by a resilient boot and retainer assembly. The piston which forces the friction elements against the friction faces of the rotor is provided with a circumferentially extending groove which receives the bead circumscribing one end of the boot. The bead circumscribing the other end of the boot is clamped against a land of the piston by a boot retainer.
U.S. Pat. No. 4,039,053 to Meyer, et al., discloses in a disk brake in which a moveable member is slidably mounted on a fixed support member by means of at least one column at least one protecting device is associated to each column to prevent various particles such as mud, grease, and the like to be deposited on the sliding surfaces of the column. The protecting device includes a seal of resilient material which cooperates with the outside surface of the column by means of at least one lip, and which carries a rigid scraper element level with the outside surface of the column. The scraper element is mounted outside with respect to the lip of the seal to clean off the particles of solid materials in a first stage, the liquid particles being retained by the lip in a second stage.
U.S. Pat. No. 3,631,767 to Meier, discloses a disk brake wheel cylinder in which the open end of the cylinder is protected by a wear and corrosion resistant insert in the form of a collar which is retained by a groove in the wall of the cylinder.
U.S. Pat. No. 3,476,221 to Schanz, discloses a piston cylinder assembly with seal means and corrosion preventing means.
U.S. Pat. No. 3,478,650 to Schrader, et al., discloses in a piston and cylinder assembly for an automotive spot-type disk brake a recess is provided in the wall of the cylinder bore for the deposition of particles detached from the dust cap and the packing material, to prevent the agglomeration of such matter in the space between the piston and the cylinder wall where it is apt to interfere with trouble free piston motion.
U.S. Pat. No. 3,490,343 to Afanador, et al., discloses a combined piston boot seal and wiper encircles the hydraulic cylinder in a disk brake and includes an integral wiper which rides on the outer surface of the piston inwardly of a bellows type boot seal providing dual protection for the piston surface and for the cylinder bore from road hazards, contamination and the like.
Presently there lacks a disk brake caliper assembly that is designed to address anticipated brake piston corrosion of trailers used in harsh corrosive environments.